Monitoring pharmacological therapy for osteoporosis

Monitoring of osteoporosis therapy

Over the past two decades, major advances have been made in the number and range of agents available for the treatment of osteoporosis, all with proven anti-fracture efficacy. Unfortunately, compliance with these treatments is not optimal, and a number of patients could be considered as non-responders. Consequently, monitoring anti-osteoporotic therapy could be part of successful osteoporosis management. Currently, no formal well-accepted clinical practice guidelines are available for monitoring anti-osteoporosis therapies. Changes in bone mineral density and bone turnover markers, while on therapy, have potential value in monitoring treatment but their assessment and, consequently, their benefits could be limited by metrological and clinical issues. Moreover, their effectiveness is probably drug dependant. Recommendation for the standardisation of the methodology when analysing the potential relevance of tools for the monitoring of osteoporosis therapy is needed.

Treat-to-target for osteoporosis: is now the time?

OBJECTIVES

Current clinical practice guidelines identify patients at high risk for fracture who are likely to benefit from pharmacological therapy and suggest ways to monitor for effectiveness of therapy. However, there is no clear guidance on when fracture risk has been reduced to an acceptably low level. As a consequence, some patients at low risk for fracture may be treated for longer than necessary, whereas others at high risk for fracture may have treatment stopped when they might benefit from continuation of the same treatment or a change to a more potent therapeutic agent. The objective of this statement is to describe the potential clinical utility of developing a "treat-to-target" strategy for the management of patients with osteoporosis.

PARTICIPANTS

We recommend that a task force of clinicians, clinical investigators, and other stakeholders in the care of osteoporosis explore the options, review the evidence, and identify additional areas for investigation to establish osteoporosis treatment targets.

EVIDENCE

Data from large, prospective, randomized, placebo-controlled registration trials for currently available osteoporosis therapies should be analyzed for commonalities of correlations between easily measured endpoints and fracture risk.

CONSENSUS PROCESS

Osteoporosis experts, professional organizations, and patient care advocates should be involved in the process of developing consensus on easily measurable osteoporosis treatment targets that are supported by the best available evidence and likely to be accepted by clinicians and patients in the care of osteoporosis.

CONCLUSIONS

A treat-to-target strategy for osteoporosis offers the potential of improving osteoporosis care by reducing the burden of osteoporotic fractures and limiting adverse effects of therapy.

Bone density testing intervals and common sense

Measurement of bone mineral density (BMD) is underutilized, contributing to the underdiagnosis and undertreatment of osteoporosis. Appropriate patient selection for BMD testing leads to more people being treated, fewer fractures, and a decrease in fracture-related health care costs. Although there are well-established indications for BMD testing, it is less clear when a BMD test should be repeated for a patient who does not have osteoporosis and is found to be at low fracture risk with initial testing. BMD testing intervals should be individualized according to the likelihood that the results will influence treatment decisions.

Clinical use of bone turnover markers to monitor pharmacologic fracture prevention therapy

Monitoring of drug therapies to prevent fractures is controversial. Measurement of bone turnover markers has the potential to identify those with a suboptimal response to fracture prevention medication within a few months of its commencement. However, given the imprecision of currently commercially available assays of bone turnover markers, many individual persons who are “suboptimal medication responders” are likely to be misclassified as “adequate responders” or vice versa, depending on the cut point chosen to define suboptimal and adequate response. Before bone turnover markers can be recommended for routine use in clinical practice to monitor fracture prevention therapies, three advances are needed: 1) bone marker assays with better precision; 2) research establishing optimal cut points of bone marker levels to distinguish “suboptimal responders” from “adequate responders”; and 3) research establishing the incremental fracture reduction benefit from clinical interventions for “suboptimal responders” identified from bone marker measurements.

Current and emerging therapies for the treatment of osteoporosis

Osteoporosis represents a weakening of bone tissue due to an imbalance in the dynamic processes of bone formation and bone resorption that are continually ongoing within bone tissue. Most currently available osteoporosis therapies are antiresorptive agents. Over the past decade, bisphosphonates, notably alendronate and risedronate, have become the dominant agents with newer bisphosphonates such as ibandronate and zoledronic acid following a trend of less frequent dosing regimens. Synthetic estrogen receptor modulators (SERMs) continue to be developed as drugs that maintain the bone-protective effects of estrogen while avoiding its associated adverse side effects. Currently available agents of this class include raloxifene, the only SERM available in the United States (US), and lasofoxifene and bazedoxifene, available in Europe. Calcitonin, usually administered as a nasal spray, completes the list of currently approved antiresorptive agents, while parathyroid hormone analogs represent the only anabolic agents currently approved in both the US and Europe. Strontium ranelate is an additional agent available in Europe but not the US that has both anabolic and antiresorptive activity. New agents expected to further expand therapeutic options include denosumab, a monoclonal antibody inhibitor of the resorptive enzyme cathepsin K, which is in the final stages of Food and Drug Administration approval. Other agents in preclinical development include those targeting specific molecules of the Wnt/β-catenin pathway involved in stimulating bone formation by osteoblast cells. This review discusses the use of currently available agents as well as highlighting emerging agents expected to bring significant changes to the approach to osteoporosis therapy in the near future.